Lubricants containing metal compounds of n, n&#39;-substituted dithiooxamides



United States Patent 0 3,252,910 LUBRICANTS CONTAINING METAL COMPOUNDS0F N,N-SUBSTITUTED DITHIOOXAMIDES Edward A. Oberright, Woodbury, N.J.,assignor to Sgocofiny Mobil Oil Company, Inc., a corporation of New orNo Drawing. Filed July 1, 1963, Ser. No. 292,132 19 Claims. (Cl.25242.7)

The present invention relates to lubricating oil compositions possessingimproved characteristics.

More particularly, the invention concerns improved lubricating oilcompositions containing certain complexes of N,N'-substituteddithiooxamides.

It is well known that lubricating oils are subject to oxidativedegradation under conditions of use in modern combustion engines.Oxidative combustion products of an acid nature are formed in thelubricants during engine operation and exert a corrosive elfect on themetal parts with which the lubricants come in contact. In addition,these oxidative products tend to produce formations of varnish or sludgeon the engine which lower its operating eificiency. In order to lessen,as far as possible, these undesirable effects, anti-oxidant compoundsare added to the lubricating oils.

It is further recognized that many lubricating oils, because of theirparticular nature and characteristics, often possess unsatisfactoryviscosity indices (V.I.), that is, viscosity changes too rapidly withinthe operating temperature ranges of the engine. These oils thereforealso require the presence of additives which act to improve their V.I.characteristics.

According to the present invention, it has been found that it ispossible to inhibit the oxidative degradation of lubricating oilcompositions as Well as improve the viscosity indices thereof by addingto these compositions certain complexes of N,N-substitu'teddithiooxamides.

Thus, by employing these complexes of N,N-substituted dithiooxamides itis possible to produce lubricating oils possessing both superioroxidation stability and improved V.I. characteristics without resortingto the use of separate anti-oxidants and V.I. improver compounds.

Accordingly, it is an object of the present invention to providelubricating oil compositions possessing both improved anti-oxidationcharacteristics and improved viscosity indices.

Another object is to provide a simple and effective method for improvingthe oxidation resistance and the V.I. characteristics of lubricatingoils.

Other objects of the invention and the advantages thereof, will becomeapparent from the following detailed description.

The combination anti-oxidant and V.I. improver compounds of thisinvention are metal complexes of N,N- disubstituted dithiooxamides.

The preparation and possible structure of these metal complexes isdescribed by Hurd et al. at pages 4454-4458 of the Journal of theAmerican Chemical Society, vol. 82, 1960.

Although the invention is not limited to any particular theory regardingthe structure of these complexes it is believed that they have thefollowing structural formula:

wherein M is a metal; n has a value of at least 1, preferably from 6 to10; and R and R each represents an organic radical, either the same ordiiferent, containing sufficient carbon atoms to impart oil solubilityto the metal complex, which organic radical is directly attached to thenitrogen atom by a carbon atom of said organic radical containing atleast one hydrogen atom.

Examples of suitable organic radicals include hydrocarbyl radicals suchas saturated or olefinically-unsaturated, straight chain or branchedchain aliphatic radicals, which radicals are directly attached to thenitrogen atoms through carbon atoms of these radicals containing atleast one hydrogen; cycloalkyl radicals; and aralkyl radicals I whichare attached to the nitrogen atoms by a non-tertiary carbon of the alkylsubstituent, i.e., a carbon containing at least one hydrogen. Furtherexamples of suitable organic radicals include hydrocarbyl' radicals ofthis type additionally containing at least one hydroxy, amino, 30 imino,alkoxy or carboxy group.

It will be noted from the above that aliphatic radicals which areattached to the nitrogen atoms through a tertiary carbon atom, andphenyl groups directly attached to the nitrogen atoms are excluded fromthe sope of R 35 and R.

The term organic radical, as used herein, is employed in its genericsense and covers both hydrocarbyl radicals per se and hydrocarbylradicals further containing additional groups such as the aforementionedhydroxy, amino, imino, alkoxy and carboxy groups.

As some preferred examples of organic radicals which may be present asthe N,N-substituted components there may be mentioned; octyl, decyl,dodecyl, tetradecyl, hexadecyl, octadecyl, octadecenyl, cyclohexyl,benzyl, carboxyl-hexyl, hyd r-oxy-octyl, and n-oleyl propyl amineradicals.

In general, the organic radicals present as the N,N'-

substituted groups contain a total of at least 5 carbons preferably from5 to about 30 carbon atoms. 5 M may be selected from a wide variety ofsuitable metals. Metals from Groups I, II, VI and VIII of the MendeleffPeriodic Table, especially Group II and VIII metals are particularlysuitable. Some preferred examples of such metals are silver, copper,calcium, zinc, mercury, molybdenum, nickel, cobalt, iron, ruthenium,platinum and palladium.

Briefly, the N,N'-substituted dithiooxamido metal complexes, employedaccording to the present invention, may be prepared by reacting at leastabout two equivalents of the salt, hydroxide or oxide of the desiredmetal, pref- J erably in the presence of a base, with anN,N'-substituted dithiooxamide of the formula:

H s H RI I(L il IR (A) wherein R and R have the above meaning. Thisreaction is preferably conducted in an absolute alcoholic solution atroom temperature or higher. Although any soluble metal salt, hydroxideor oxide may be employed in the synthesis reaction, metal halides, metalcarbonates, metal acetates and metal nitrates are preferred.

The N,N-substituted dithiooxamides of Formula A can be obtained byreacting dithiooxamide with primary amines or mixtures of primaryamines. Suitable amines include, aliphatic cycloalkyl and aralkylprimary amines wherein the nitrogen of the primary amamine is attachedto a carbon atom containing at least one hydrogen atom. Primary amineswherein the amino nitrogen is directly attached to a phenyl group or atertiary carbon of a tertiary alkyl group are not suitable.

The metal complexes of the N,Nsubstituted dithiooxamides employedaccording to the present invention may be present as relatively pureindividual compounds, or as mixtures of two or more metal complexes ofthis type wherein the complexes contain a variety of N,N- substitutedorganic radicals.

Thus, for example, when the N,N-substituted dithiooxamides used in thepreparation of the instant metal complexes, are obtained by the reactionof dithiooxamide with a mixture of suitable primary aliphatic aminescontaining from about 8 to 18 carbon atoms, mixtures of N,N-substituteddithiooxamido metal complexes containing various aliphatic groups as theN,N'-substitutents, are obtained. The proportions of these variousN,N-substituted metal complexes in the mixture generally depends on theproportions of the different primary aliphatic amines in said aminemixture. In this particular case the mixture primary aliphatic aminescontains the following proportions:

For convenience, the above-described primary amine mixture is hereinreferred to as C C mixture, and the corresponding metal complexes ofN,N'-substituted dithiooxamides obtained from N,N-substituteddithiooxamides prepared using said amine mixture, are termed metalcomplexes of N,N'-bis (C -C dithiooxamides.

Similarly, metal complexes obtained from N,N-substituted dithiooxamidesprepared from dithiooxamide and amine compositions exhibiting an iodinevalue of about 60, a specific gravity at 25 C. of 0.841, and containingabout 80% of diamines of the formula,

H H H R"N-C-CONH H H H H H wherein R" is derived from oleic acid and issubstantially composed of the oleyl group (C are herein referred to asN,N'-bis (N-C propyl amine) dithiooxamide metal complexes.

Further details as to the preparation of the metal complexes are givenin the above-mentioned Hurd et al'. article.

The metal complexes of N,N'-disubstituted dithiooxamides when added tolubricating oils act to improve the characteristics of the oils in atleast two primary ways. They inhibit the deterioration of the oil due tooxidation, thus lessening or eliminating both the formation of sludgeand the damage caused by the attack of acidic oxidation products on themetal surfaces to be lubricated. In addition, these metal complexes actto increase the viscosity index (V.I.) of the composition therebyreducing any changes in the viscosity of the oils normally caused bytemperature variations.

The particular amounts of metal complexes added to the lubricating oilswill depend on the particular nature of the base oil, the presence orabsence of other additives and the uses to which the lubricating oilsare to be put.

In general, from about .001% to 10%, preferably from about 0.1 to 2.0%may be used.

The N,N'-disubstituted dithiooxamido metal complexes may beadvantageously employed in a variety of lubricating oil compositions.

Some examples of lubricating oils, both petroleum base oils andsynthetic oils, e.g., synthetic hydrocarbon and synthetic ester, theoxidation stability and V1. of which may be improved include mineraloils from different crudes both solvent and acid refined, hydrocracked,etc. Synthetic hydrocarbon oils would include hydrogenated polyolefins,alkyl benzene, etc. Synthetic esters would include di-Z-ethylhexylsebacate, di-octyh adipate, trimethylol propane trioctanoate,pentaerythritol tetraheptanoate, etc.

The compositions of the present invention may, of

course, also contain effective quantities of various typical additives,normally used in lubricating oils which are designed to improve the oilcompositon in other respects, such as detergents, rust inhibitors,pourpoint improvers, etc.

The following specific embodiments will serve to further illustrate thepresent invention.

PREPARATION OF N,N-DISUBSTITUTED DI- THIOOXAMIDE METAL COMPLEX Thepreparation of the zinc complex of N,N-dioctadecyl dithiooxamide isgiven as illustrative of a suitable method for the preparation of themetal complexes.

An absolute ethanol solution of two equivalents of ZnCl and fourequivalents of triethylamine is filtered, warmed to 60 C. and addeddropwise to a well-stirred, absolute ethanol solution of one equivalentof purified N,N-dioctadecyl dithiooxamide which is maintained at 70 C.during the addition period. The resulting product is both an oil and atan solid. The oil readily solidifies upon cooling. The product,including the additional material gained on concentration of the motherliquor, is triturated, washed with acetone and Soxhlet-extracted withethanol for 24 hours and then dried under vacuum (about .1 mm. 65 F.).

Upon analysis this product contains: 4.5% N, 8.6% S and 9.8% Zn.

Some examples of other suitable metal complexes and their respectivemetal, sulfur and nitrogen contents, whe e available, are as follows:

Examples 1-11 The oil compositions shown in the following Table 1 areprepared.

In order to determine the effect of the metal complexes on the viscositycharacteristics of the oil compositions, the K.V. of each composition isobtained at 5 F. and 210 F. and the viscosity index (V.I.) is calculatedtherefrom.

The initial and final neutralization numbers (N.N.) for each oilcomposition are reported in Table 2.

TABLE 1.-MEIAL COMPLEXES AS V.I. AGENTS Additive Initial Example Cone.

No. Composition (weight percent) K.V. at K.V. at V.I.

Base Oil A 8.91 62. 98 111 Base Oil A plus Zn Complex of N,N-dioctadecyldithiooxamide-.. 3.0 19. 19 103. 9 147 1. 5 11. 54 72. 7 139 i 0.75 9.30 65.9 123 Base Oil A plus Zn Complex of N,N'-Bis (Cs-01B)dithiooxamiden 3. 67.25 767.0 123 do 1. 21. 19 210. 0 118 do 0.75 11. 4283.1 126 Base Oil B 5. 44 34. 03 104 Base Oil B plus Zn Complex of N,N-dioctadecyl dithiooxamide. 3. 0 23. 78 299. 8 122 8.-.- 1.5 10.53 87.28 111 9 0.75 7.42 52. 92 110 10 Base Oil B plus Zn Complex of N ,N-(C-Cia) dithiooxamido 1. 5 25. 87 277 118 11 do 0. 75 12. 01 109. 9 106 lA SAE grade, solvent-refined oil having a K.V. of 8.91 cs. at 210 F. and62.98 cs. at

1 Illend of 80% mid-continent distillate and 20% naphthenic distillatecontaining 3.3%

barium sulionate and 3.3% barium phenate.

From the viscosity indices reported in Table 1, it will be noted thatthe metal complexes improve the V.I. of each of the oil compositions.

Examples 12-24 The oil compositions shown in Table 2 are prepared byadmixing the dithiooxamido metal complexes and various base oil stocks.

CATALYTIC OXIDATION TEST In order to determine the effectiveness ofthese metal complexes in inhibiting the oxidation of the oils, the com-The difference between the initial N.N. of the oil and the N.N. of theoil after being subjected to oxidation according to the test procedureis an -indication of the ing no metal complex.

tralization number than the corresponding oils contain- These low finalneutralization numbers indicate that that the oils of the presentinvention containing N,N'-disubstituted dithiooxamido metal complexespossess superior resistance to oxidative degradation.

TABLE 2.OATALYTIC OXIDATION TEST AT 325 F. FOR 24 HOURS Additive Neut. N0. Example Composition Cone.

N 0. (weight percent) Initial Final Base Oil A 1 10 12 Base Oil A plusZn Complex of N,N- 3. 0

dioctadecyl dithiooxamide. 1% do 1. 0 l4 dn 8. 3 15 Base Oil A plus ZnComplex of N,N-bis 0. 2. 8

(Ce-C15) dithiooxamide. 16. do 0.15 2. 3 17- rlr 0.15 1.9 Base Oil C 20.13 3. 3 18 Base Oil C plus 00 Complex of N,N- 0. 20 0. 20

diodecyl dithiooxamide. Base Oil D 3 0. 18 35. 4 19 Base Oil D plus ZnComplex of N,N- 0. 1 0.38

dioctadecyl dithiooxamide. 20. do 0. 38 21 do 0.63 22 Base Oil D plus ZnComplex of N,N-bis 0. 25

(CB-Cl!) dithiooxamido. 23 (in 0.50 24.. rln 0. 38

1 See Table 1. 2 Trimethylolpropane triootanoate. Di-2-ethyl hexylsebacate.

positions of Examples 12-24 are subjected to a catalytic oxidation test.

According to this procedure, 25 cc. of the test oil is placed in .a 200x 25 mm. test tube with 15.6 sq. in. of sandblasted iron wire, 0.78 sq.in. of polished copper wire, 0.87 sq. in. of polished aluminum wire, and0.167 sq. in. of polished lead surface. Dry air is passed through thesample at the ratio of 10 liters per hour while the samples are heatedin an aluminum block bath for a period of 24 hours at a temperature of325 F.

Examples 25-32 The metal complexes are admixed With a synthetic esterbase oil comprising di-2-ethylhexyl sebacate in the 0 amounts shown inTable 3.

The resulting oil compositions are then subjected to the catalyticoxidation test described above.

The initial and final neutralization numbers, and the initial and finalK.V. at 210 F. for each of the oil sampics is determined and reported inTable 3.

It will be noted that the neutralization number of the blank oilcontaining no metal complex increases from 0.18 to 35.4, whereas theoils containing the metal complexes exhibit significantly superioroxidation stability as evidenced by the slight diiference between theirinitial and final neutralization numbers.

TABLE 3.CATALYTIC OXIDATION TEST AT 325 F. FOR 24 HOURS Additive Neut.No. K.V. at 210, cs. Example Composition Cone.

No. (weight percent) Initial Final Initial Final Base Oil D 1 0.18 35. 43. 35 6. 27 25 Base Oil D plus Zn Complex of N,N- 0.5 0.05 0.8 3. 40 3.41

blS(Ca-Cis) dithiooxamide. 26 do 0. 25 0. 05 1. 0 3. 38 3. 40 27 BaseOil D plus Zn Complex of N,N- 0.5 0.45 0.8 3.37 3. 55

bis(N-C1s propyl amine) dithiooxamide. 2s (In 0.25 0. 20 14. 3 3. 35 4.30 29 Base Oil D plus Co Complex of N,N- 0.5 0.10 0.50 3. 88 3. 40

bis(dehydroabietyl) dithiooxamide. do 0.25 0.10 0. 50 3.37 3. 39 31 BaseOil D plus Ni Complex 0! N ,N- 1. O 0. 0.8 3. 42 3.51

bis(dehydroabietyl) dithiooxamide. i2 rln 0. 5 0.15 0.5 3. 38 3. 39

1 Di-2-ethylhexyl sebacate.

Examples 33-40 metal of said complex 18 selected from the class consist-Eight oil compositions containing the metal complexes are prepared.

These oils are then subjected to the catalytic oxidation test describedabove. The results obtained including the amount of lead lost from thelead surface is reported in Table 4.

ing of Groups I, II, VI and VIII of the Mendeleff Periodic Table andwherein the N,N'-di-substituted group is an organic radical selectedfrom the group consisting of hydrocarbyl radicals and substitutedhydrocarbyl radicals directly attached to the nitrogen atom by a carbonatom containing at least one hydrogen atom, and which TABLE 4.CATALYTICOXIDATION TEST AT 825 F. FOR 24 HOURS Additive Neut. No. K.V. at 210,cs. Lead Example Composition Cone. Loss,

NO. (weight) mg.

percent) Initial Final Initial Final Base Oil A 1 0. 10 12. 8 8. 38 17.85 200 33 Base Oil A plus Zn Complex of N,N-b1s (oleyl) 2.0 0. l0 3. 58. 80 9. 09 7.0

dithiooxamide. 34 dn 1.0 0.10 2.8 8. 55 9.27 15. 5 35 Base Oil A plus ZnComplex of N,N-bis (N-C 1. 0 0.70 3.0 8. 47 10. 92 4. 9

propyl amine) dithiooxamide. 36-- o 0.5 0. 5. 3 8. 43 11. 25 3. 5 37..Base Oil A plus Co Complex of N,N'-b1s (dehy- 2.0 0.15 1.3 8.83 9. 36

droabietyl) dithiooxamide. 38 do 1. 0 0.15 3. 8 8. 59 10. 39 Base Oil Aplus Ni Complex of N,N'-bls (dehy- 2. 0 0.35 3.8 8.87 10.61

droabietyl) dithiooxamide. 40 n 1. 0 0. 25 4. 5 8. 57 11. 28

1 See Table 1.

From a comparison of the initial and final neutralization numbers andinitial and final K.V. values of the base oil alone and the base oilscontaining the metal complexes, it will be noted that these latter oilcompositions exhibit both superior oxidation stability and more constantviscosity characteristics. In addition, it is noted that in the casewhere the base oil alone is employed, 200 mg. of metal are lost from thelead surface due to the corrosive action of the oxidation productsformed in the oil. However, in the oil compositions of Examples 33-36which contained the metal complexes, the formation of oxidation productsis inhibited to such an extent that only from 3.5 to 16 mg. of metal arelost.

Although the present invention has been described by reference tocertain preferred embodiments, it is to be understood that modificationsand variations may be resorted to, without departing from the spirit andscope of this invention.

Having thus described the invention what it is desired to secure andclaim by Letters Patent is:

1. A lubricating composition comprising a major proportion of alubricating oil and a minor proportion sufiicient to improve theoxidation stability and viscosity index thereof of at least one oilsoluble metal complex of an N,N-organo-di-substituted dithiooxamidewherein the organo radical is selected from the group consisting oforganic radical contains sufiicient carbon atoms to render theN,N'-di-substituted dithiooxamido metal complex oilsoluble.

3. The lubricating composition of claim 2, wherein said organic radicalscontain from 5 to about 30 carbon atoms.

4. The lubricating composition of claim 2, wherein the organic radicalis a hydrocarbyl radical containing at least one member selected fromthe class consisting of hydroxy, amino, imino, alkoxy and carboxygroups.

5. The lubricating composition of claim 2, wherein the organic radicalis an aliphatic radical.

6. The lubricating composition of claim 2, wherein the organic radicalis a cycloalkyl radical.

7. The lubricating composition of claim 2, wherein the organic radicalis an aralkyl radical.

8. The lubricating composition of claim 2, wherein the metal componentof said metal complex is a Group II metal.

9. The lubricating composition of claim 2, wherein the metal componentof said metal complex is a Group VIII metal.

10. The lubricating composition of claim 2, wherein theN,N-di-substitutcd dithiooxamido metal complex is present in an amountfrom about 0.001 to about 10% by weight.

11. The lubricating composition of claim 2, wherein the lubricating oilis a mineral oil.

12. The lubricating composition of claim 2, wherein the lubricating oilis a synthetic ester oil.

13. The lubricating composition of claim 2, wherein the lubricating oilis a synthetic hydrocarbon oil.

14. A lubricating oil composition comprising a major proportion of alubricating oil and from about 0.001 to about 10% by weight ofN,N-dioctadecyl dithiooxamido ZlIlC.

15. A lubricating oil composition comprising a major proportion of alubricating oil and from about 0.001 to about 10% by weight ofN,N'-dioleyl dithiooxamido zinc.

16. A lubricating oil composition comprising a major proportion of alubricating oil and from about 0.001 to about 10% by weight ofN,N'-bis(dehydroabietyl) dithiooxarnido cobalt.

17. A lubricating oil composition comprising. a major proportion of alubricating oil and from about 0.001 to about 10% by weight ofN,N-didodecyl dithiooxamido 20 cobalt.

18. A lubricating oil composition comprising a major.symmetrical-N,N'-hydrocarbyl radical and a symmetrical- N,N-substitutedhydrocarbyl radical.

References Cited by the Examiner UNITED STATES PATENTS 4/1940 Reifi25242.7 10/1949 Watson et al. 252--47 OTHER REFERENCES Martell et al.,Chemistry of the Metal Chelate Compounds (1952), p. 503.

DANIEL E. WYMAN, Primary Examiner.

C. F. DEES, Assistant Examiner.

1. A LUBRICATING COMPOSITION COMPRISING A MAJOR PROPORTION OF ALUBRICATING OIL AND A MINOR PROPORTION SUFFICIENT TO IMPROVE THEOXIDATION STABILITY AND VISCOSITY INDEX THEREOF OF AT LEAST ONE OILSOLUBLE METAL COMPLEX OF AN N,N''-ORGANO-DI-SUBSTITUTED DITHIOOXAMIDEWHEREIN THE ORGANO RADICAL IS SELECTED FROM THE GROUP CONSISTING OFHYDROCARBYL RADICALS AND SUBSTITUTED HYDROCARBYL RADICALS.